Hin Sarai

The site is a rock stack of stromatolitic limestone exposed in a rubber plantation near the Khao Noi area. It is similar to a large termite mound but instead it is an outcrop of thin-bedded limestone of the Pa Kae Formation extended from its type locality. It has been protected by a structure with shelter from sunlight and rain. It is a red thin-bedded limestone with beds dipped toward the south ranging in thickness from 10 to 20 centimeters. No any fossils have been reported but Late Ordovician can be said in term of a stratigraphic correlation.

Stromatolites (/strˈmætəlts, strə-/[1][2]) or stromatoliths (from Greek στρῶμα strōma "layer, stratum" (GEN στρώματος stromatos), and λίθος lithos "rock")[3] are layered bio-chemical accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms (microbial mats) of microorganisms, especially cyanobacteria.[4] Fossilized stromatolites provide ancient records of life on Earth by these remains, some of which may date from 3.7 billion years ago.[5][6] Lichen stromatolites are a proposed mechanism of formation of some kinds of layered rock structure that are formed above water, where rock meets air, by repeated colonization of the rock by endolithic lichens